Adjusting BLM's/AFR
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Joined: May 2011
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From: Corvallis, OR
Car: 87 Iroc
Engine: 5.7L TPI
Transmission: Built 700R4
Axle/Gears: 3.23 posi
Adjusting BLM's/AFR
Hey everyone, i am still trying to learn everything i can about tuning the prom. its hard to fit in with engineering classes though 
my question for eveyone is:
would it be beneficial for fuel mileage to set a target AFR for something like 15-15.1? i do all highway and about a mile city on each side of my commute and its all flat. if i set a ratio of 15, would i have to readjust BLM's back to 128 or would that negate the higher ratio?
Thanks
my question for eveyone is:would it be beneficial for fuel mileage to set a target AFR for something like 15-15.1? i do all highway and about a mile city on each side of my commute and its all flat. if i set a ratio of 15, would i have to readjust BLM's back to 128 or would that negate the higher ratio?
Thanks
Re: Adjusting BLM's/AFR
Your ECU already provides a DFCO as well as highway mode.
It can be edited for A/F and other parameters.
In general CL you can enlean as well. Keep in mind E10 is like 14.2-14.3/1. good gas is 14.7/1. There is a lenghty rite up in stickies.
search Raucher.
It can be edited for A/F and other parameters.
In general CL you can enlean as well. Keep in mind E10 is like 14.2-14.3/1. good gas is 14.7/1. There is a lenghty rite up in stickies.
search Raucher.
Last edited by Ronny; Mar 12, 2012 at 11:26 AM.
Thread Starter
Junior Member
Joined: May 2011
Posts: 94
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From: Corvallis, OR
Car: 87 Iroc
Engine: 5.7L TPI
Transmission: Built 700R4
Axle/Gears: 3.23 posi
Re: Adjusting BLM's/AFR
i have adjusted BLM's to 128 with a 14.76 AFR, enabled highway mode to 16.3 in my main highway load range, and have DFCO and Decel enlean enabled. with all of those i am still getting 16.5 mpg on the highway. i was wondering where else i could squeeze out mileage. i am shooting for at least 20 highway.
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From: Idaho
Thread Starter
Junior Member
Joined: May 2011
Posts: 94
Likes: 0
From: Corvallis, OR
Car: 87 Iroc
Engine: 5.7L TPI
Transmission: Built 700R4
Axle/Gears: 3.23 posi
Re: Adjusting BLM's/AFR
Are you saying with E10 fuel the stoich ratio should be changed? I will look for the writeup...
Re: Adjusting BLM's/AFR
That I dont know. It uses stoich value for one or more of the calcs. It may use stoich value for OL calc. Not sure. the mean lean rich 02 values I believe are used for CL calcs to provide the PW result.
need to read the sticky on prop gains. thread I recall started by me. Raucher posted his write up in it. Explained there.
need to read the sticky on prop gains. thread I recall started by me. Raucher posted his write up in it. Explained there.
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From: Pacific NW
Car: 89 K3500 Fleetside
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Transmission: TH400
Axle/Gears: 3.73-Dana 60
Re: Adjusting BLM's/AFR
In order to actually change CL AFR it's necessary to change the o2 voltage targets.
Re: Adjusting BLM's/AFR
I puller this out of Raucher paper.
STOICH:
The value labeled 'stoich' needs to match the O2 sensor AFR switch
point. On the '747, this value is located at: 0x2AA. The value is 147,
for 14.7 AFR.
Conjecture: This stoich value, plus the R/L O2 error boundries, define
the O2 sensor output levels. This ties the O2 sensor calibration into
the PW equation.
As the R/L O2 Error Boundries define actual O2 sensor stoich switch
point in output volts. The 14.7 AFR switch point of the O2 sensor is
now 'calibrated' into the PW calculation.
If a different fuel is used, with say a stoich value of 16.1, by
placing the value of 161 at 0x2AA, the PW is again calibrated for
that fuel. If you now want to command the ecm to change the PW enough
for a 15.3 AFR, by using 153 in the PW calculation, the PW will
be increased the proper amount to produce that AFR (in open loop).
Remember that when in closed loop, the stoich value is used in
the PW calculation. In open loop, the desired AFR is used in the
PW calculation (say, when it's 5 degrees out, and the engine is
first started, the desired AFR might be 9.0).
Another example: Say a new O2 sensor was developed, for gasoline,
that costs $3.00. Good deal. However, the stoich switch point output
voltage is at 625mV, opposed to the current sensors switch point of 450mV.
By changing the R/L O2 error boundry table values, this new O2 sensor
can be calibrated for the PW calculation. Instead of the tables
straddling the 450mV value, set the table values to straddle the new
625mV O2 sensor value.
The value labeled 'stoich' needs to match the O2 sensor AFR switch
point. On the '747, this value is located at: 0x2AA. The value is 147,
for 14.7 AFR.
Conjecture: This stoich value, plus the R/L O2 error boundries, define
the O2 sensor output levels. This ties the O2 sensor calibration into
the PW equation.
As the R/L O2 Error Boundries define actual O2 sensor stoich switch
point in output volts. The 14.7 AFR switch point of the O2 sensor is
now 'calibrated' into the PW calculation.
If a different fuel is used, with say a stoich value of 16.1, by
placing the value of 161 at 0x2AA, the PW is again calibrated for
that fuel. If you now want to command the ecm to change the PW enough
for a 15.3 AFR, by using 153 in the PW calculation, the PW will
be increased the proper amount to produce that AFR (in open loop).
Remember that when in closed loop, the stoich value is used in
the PW calculation. In open loop, the desired AFR is used in the
PW calculation (say, when it's 5 degrees out, and the engine is
first started, the desired AFR might be 9.0).
Another example: Say a new O2 sensor was developed, for gasoline,
that costs $3.00. Good deal. However, the stoich switch point output
voltage is at 625mV, opposed to the current sensors switch point of 450mV.
By changing the R/L O2 error boundry table values, this new O2 sensor
can be calibrated for the PW calculation. Instead of the tables
straddling the 450mV value, set the table values to straddle the new
625mV O2 sensor value.
Re: Adjusting BLM's/AFR
I think this is the key: The use of fuel. In WI we have reg gas, E10 and soon E15. So you need to place in that constant what fuel is being used.
"If a different fuel is used, with say a stoich value of 16.1, by
placing the value of 161 at 0x2AA, the PW is again calibrated for
that fuel. If you now want to command the ecm to change the PW enough
for a 15.3 AFR, by using 153 in the PW calculation, the PW will
be increased the proper amount to produce that AFR (in open loop)."
"If a different fuel is used, with say a stoich value of 16.1, by
placing the value of 161 at 0x2AA, the PW is again calibrated for
that fuel. If you now want to command the ecm to change the PW enough
for a 15.3 AFR, by using 153 in the PW calculation, the PW will
be increased the proper amount to produce that AFR (in open loop)."
Thread Starter
Junior Member
Joined: May 2011
Posts: 94
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From: Corvallis, OR
Car: 87 Iroc
Engine: 5.7L TPI
Transmission: Built 700R4
Axle/Gears: 3.23 posi
Re: Adjusting BLM's/AFR
i am using '165 6E and all i see for O2 settings is the time to hot times and the error reduction gain vs airflow. i think i will stick with 14.7 for right now at least. i have finals next week that are going to be a b****. after that i can play around a little more. are their other settings i can adjust to get better mileage? HWM, DFCO... i haven't dived into AE or PE yet i have been working on getting BLM's and spark dialed in
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Re: Adjusting BLM's/AFR
I thought Eanything was on it's way out? Especially with the end of the subsidy?
What is CL?
From what I read on highway you can go as far as 17:1 for mileage however this negatively affects emissions.
What is CL?
From what I read on highway you can go as far as 17:1 for mileage however this negatively affects emissions.
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Joined: Oct 2002
Posts: 1,096
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From: Idaho
Re: Adjusting BLM's/AFR
Closed Loop.
Here's a start of an EFI dictionary.
http://www.gearhead-efi.com/gm-ecm-p...ictionary.html
Here's a start of an EFI dictionary.
http://www.gearhead-efi.com/gm-ecm-p...ictionary.html
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